Method of wireless signaling.



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Patented Apr. 13, 1909.

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PATENT @FFIQE.

REGINALD A. FESSENDEN, OF BRANT ROCK, MASSACHUSETTS.

METHOD OF WIRELESS SIGNALING.

Specification of Letters Patent.

Application filed July 1, 1907.

Patented April 13, 1909.

Serial No. 381,732.

To all whom it may concern:

Be it known that I, REGINALD A. FESSEN- DEN, a citizen of the UnitedStates, residing at Brant Rock, in the State of Massachusetts, haveinvented a certain new and useful Method of lVireless Signaling, ofwhich the following is a specification.

This invention relates to electric signaling, and especially to methodsof prevention of atmospheric and other disturbances, which is itsprimary object.

In the accompanying drawings forming a part of this specification Figure1 shows an arrangement of apparatus for carrying out my invention, Fig.2shows a detall of a governing device, Fig. 3 shows an arrangement ofcircuits for use in sending and Fig. & an arrangement of circuits foruse in receiving.

Great difiiculty has been experienced in wireless signaling on accountof electric disturbances, more particularly atmospheric disturbances. Inthe tropics, for example, stations equipped with the usual type ofapparatus as a rule are unable to work at all for months at a timeexcept at brief intervals and even in the more northern climates thesame difliculties occur during the summer months. By my apparatus andmethod herein described I succeed in annulling the effects ofdisturbances, and more particularly such atmospheric disturbances.

In Fig. 1, 11 represents a steam turbine, 12 a throttle valve in thesteam pipe leading to the steam turbine, 13 a governing valve operatedby the electric contact device 14:. This turbine drives the alternatingcurrent dynamo 15, having a frequency higher than the usual commercialfrequencies but of a frequency suiiiciently low to be well within thelimits of audibility, (for example, a frequency of 900 is suitable forthe dynamo). 16 is a continuous current motor driven by the storagebattery 17 and having its speed regulated by the rheostat 18. The speedof this motor is governed by the vibrator reed 19 which makes and breaksthe local circuit containing the battery 20, magnet 21 and a coil woundon the armature of the motor 16 and connected to the brushes 8, 9, therate of vibration being altered at will by shifting the weight 19 on thereed. This method of governing known as the IVadsworth method, is wellknown. 22 is a set of differential gears attached to the shaft of thegoverning motor 16 and to the shaft of the turbine 11 so that if thespeed of the turbine varies from that of the governing motor 16, the arm23 carrying the contact brushes 2%, 25 will be carried forward orbackward and make contact with the contact 26 or the contact 2'? therebyoperating the valve 13 by means of the current from the battery 28flowing through the magnet coils 29 and 30, when the contacts 26, 21, or25, 27 respectively are closed. (In the view of Fig. 1 the contacts areshown turned 90 out of normal position, to show the arrangementclearly.)

In Fig. 2 is shown an alternative form of regulator for use in place ofmaking the contacts 21, 26 and 25, 27. In this the arm 23 operates bythe lever 31 to produce a pressure on the carbon plates 82, 38 andthereby vary the current in the magnets 29, 30, respectively, and thusregulate valve 13.

I show a suitable circuit for signaling in Fig. 3, where 3st shows asource of voltage, forexample an alternating current dynamo giving avoltage of 25,000 volts at a fre quency of 500 periods per second or thedynamo of Fig. 1 being used. 35 is a capacity which may consist ofcompressed air condensers. 3b is an adjustable inductance which mayconsist of a straight piece of copper wire and a sliding contact asshown. 37 is a spark gap and 38 is an antenna grounded at 39. 40 is amovable contact arm so arranged as to connect with the contacts s1 and42 according as the key is depressed or not, the key 43 actuating themovable arm I0 by means of the magnet 11. energized by the local battery4-5, at being a spring for the purpose of holding the movable contactarm 10 normally against contact d1. In this method of operating thespark passes continuously whether signals are being sent or not, thefrequency of the signals emitted being different when the key 18 isdepressed from that obtaining when the key is in its normal position.Fig. 4: shows a form of receiving device especially adapted for thiswork and forming an interference preventer. In this an antenna 17 of anysuitable type is grounded at 67, and $8 is a variable inductance, and 9a variable capacity in circuit with it. 50, 51 are primaries, and 52, 53the secondaries of variable transformers. These secondaries areconnected to the primaries 5i and 55 of a second set of variabletransformers having secondaries 58 and 59, the variable condensers 56and 57 being connected in circuit as shown. The secondaries 58, 59 ofthe second pair of variable transformers are connected so as to opposeeach other, while the condenser 60, preferably variable, and thereceiver 61 are in series with these secondaries. 02 is a potentiometerand 63, 64 are telephone receivers. 65, 66, 68, 69 are variablecondensers; but condensers 68, (59 may be omitted. The circuit 47, 48,49, 51, 06, 67 and the circuit 53, 55, 57 are preferably tuned to thefrequency which it is desired to receive, and the other circuit 47, 48,49, 50, 65, 67 and the circuit 52, 54, 56 are preferably tuned to otherfrequencies. Oscillations not in resonance divide equally between thetwo branches. The circuit 58, 60, 59, 61 may be tuned or not, and-prefer ably it is not tuned.

In experimenting with a high frequency alternator having a frequency of80,000 in order to determine the integrating effect of certain types ofreceivers, it was noted by me that when the trains of waves were brokenup into different lengths, when the trains succeeded each other at afrequency above the normal frequencies used for alternating currentwork,the signals become more distinct in the presence of atmosphericdisturbanees. It was noted for example, that in a specific case where itis impossible to determine whether the experimental station was sendingor not when the sparks succeeded each other at a frequency of 250 (beinggenerated by dynamo of approximately 125 cycles per second,) yet thesignals could be easily read when the spark frequency was raised to 900.I discovered and experimentally determined that the main reason for thiswas a physiological phenomenon, z. e. that when the higher frequencieswere being used for signaling the attention of the hearer wasconcentrated on the higher notes to such an extent that the lower noisesmade by atmospheric disturbances ceased to affeet the consciousness. Onthe other hand when the sparks were produced by alternating currents ofthe usual frequency it was impossible to concentrate the hearing uponthe signals and reception could not be accomplished. This physiologicaleffect was found by experiment to be so marked that messages could beread with the greatest of ease at a spark frequency of 900 per second,when at a spark frequency of 250 per second it is impossible to tellwhether the station was sending or not, although with the same settingsat a time when there is no atmospheric disturbances both sets of signalswere as measured by shunt on the telephone of equal strength.

Heretofore in the practice of the art, where spark frequencies have beenused as a means of obtaining selectivity, this has been done bydepending upon mechanical selectivity alone, without electrical tuningto the wave frequency or group frequency (as shown for example, byBritish Patent 28,955/90, to Brown, and later in Blondels U. S. Patent783,923 filed December 3rd, 1900, page 1, lines 83 to 37) or by thecombination of tuning electrically to the wave frequency andmechanically or electrically tuning to the group frequency; (seeFessenden U. S. Patents 7 27,825 filed June 2, 1900 and 706,742 filedJune 6, 1902; also shown later in Shoemakers U. S. Patent 749,584, filedOct. 3, 1902, and Stone 767,982, filed November 25, 1903). In all theabove cases, however, the selectivity was obtained through the use ofgroup frequencies by tuning the receiver mechanically or electrically,so that it would only respond to a given group frequency. In the presentapplication, on the other hand, the selectivity, or freedom fromdisturbance, is not obtained by mechanical or electrical tuning to thegroup frequency of 1000 sparks per second, but physiologically by makinguse of the novel physiological effect discovered by the applicant anddescribed above, which discovery has later been independentlycorroborated in a paper published in the Philosophical lllagazz'ncNovember, 1907 by Lord Rayleigh, who therein points out that thisphysiological discovery was contrary to what had theretofore beensupposed to be the case.

It is to be noted that where, as in applicants prior U. S. patent 727,331, filed March 21, 1903, group or spark frequencies as high as 500cycles per second have been used in connection with mechanical orelectrical tuning to the group frequencies, this did not involve thediscovery or use of the present physiological method of selectivity,since, with the mechanical or electrical group tuning already referredto, the disturbing frequencies were already cut out, or else produced anote of the same frequency as that to which the circuit was alreadytuned. For example, any irregular atmospheric disturbance which affectedthe receiver would cause an electrical or mechanical oscillation in thereceiver of the same group frequency as that to which the receiver wasalready tuned, in the same way as random blows on a tuning fork willcause it to vibrate at a particular definite periodicity, always givingthe same note.

Any suitable means of obtaining the desired spark frequency may be used,as for example an alternating current dynamo having a frequency of 500cycles, as above referred to. lVhile the receiver may also bemechanically tuned to the group, frequency, this is not alwaysadvantageous, and more over it is not part of the present invention,having been already shown and claimed in my prior patent No. 727,325, ofMay 5th, 1903.

In describing the indicator as resonantly unresponsive to the groupfrequency, such phrase is intended to mean an indicator which on beingaffected by aperiodic impulses does not emit a note of the groupfrequency being used.

The apparatus herein disclosed is not here claimed but is claimed in mydivisional application N 0. 450,163 filed August 25th, 1908.

Having thus described my invention and illustrated its use, what I claimas new and desire to secure by Letters Patent, is the following 1. Inthe art of wireless signaling, the method of eliminating disturbingimpulses which comprises generating waves having a definite frequency,in groups having a definite group frequency above 250 per second butwithin the limits of audibility, and re ceiving the same with anindicator resonantly unresponsive to said group frequency.

2. 1n the art of wireless signaling, the method of eliminatingdisturbing impulses physiologically by generating waves of a definitefrequency in groups having a group frequency between 250 per second andthe upper limit of audibility, receiving the same with a receiver whichis resonantly unresponsive to said group frequency, and arranging thereceiving circuits so that said disturbing impulses are divided thereinand oppose each others effects on the receiver.

In the art of wireless signaling, the method of eliminating disturbingimpulses which comprises generating waves having a definite frequency,in. groups having a definite group frequency of approximately 1000 persecond, and receiving the same with an incliator which is unresponsive,resonantly, to said group frequency.

4. In wireless signaling, the method of eliminating disturbing impulsesby cutting out a portion of the same electrically by means of tunedcircuits, eliminating another portion by means of other electricallytuned circuits so arranged that the eifects of the disturbing impulsesoppose each other, and finally eliminating the balance of the disturbingimpulses physiologically by using a group frequency for the signalimpulses higher than 125 per second but within the limits of audibility.

In testimony whereof I have hereunder signed my name in the presence ofthe sub scribed witnesses.

REGINALD A. FESSENDEN.

Vitnesses THOMAS B. BLACKMAN, JESSIE E. BENT.

